Anti-wetting coating for Si-based MEMS fluidic device, and method of application of same

Abstract

A photo-patterned fluorocarbon monolayer directly grafted to Si surface atoms provides anti-wetting performance at controlled locations, wherein the Si surface oxide is etched and reacted with fluorocarbon chains with a terminal C—C double bond, resulting in Si—C surface. As the direct Si—C linkages are chemically robust, and much more resistant to decomposition than Si—O—C bonds, the resulting surface does not suffer from the shortcomings of current MEMS dispensers.

The invention claimed is: 
     
       1. A method for coating a silicon substrate on a microelectromechanical system fluid dispenser including one or more nozzles, the method comprising:
 removing an oxide layer from a surface of the silicon substrate, the surface of the silicon substrate including an area around the one or more nozzles; and 
 treating a portion of the surface of the silicon substrate with radiation to react the portion of the surface of the silicon substrate with C═C—CH 2 —CF 2 —CF 2 —CF 3 , 
 wherein the area of the surface of the silicon substrate around the one or more nozzles is not treated with the radiation. 
 
     
     
       2. The method of  claim 1 , wherein the removing the oxide layer includes treating the silicon substrate with a hydrogen fluoride compound. 
     
     
       3. The method of  claim 1 , wherein the radiation is selected from the group consisting of UV light, electromagnetic radiation, thermal radiation, infrared (“IR”), derivatives thereof, and combination therefrom. 
     
     
       4. The method of  claim 3 , further comprising positioning a photomask between the surface of the silicon substrate and the radiation such that the portion of the surface of the silicon substrate is treated with the radiation and the area of the surface of the silicon substrate around the one or more nozzles is not treated with the radiation. 
     
     
       5. The method of  claim 3 , further comprising adding a sacrificial electron acceptor to accelerate the reacting the portion of the surface of the silicon substrate with the C═C—CH 2 —CF 2 —CF 2 —CF 3 . 
     
     
       6. The method of  claim 1 , further comprising controlling a degree of reaction of the portion of the surface of the silicon substrate with the C═C—CH 2 —CF 2 —CF 2 —CF 3 . 
     
     
       7. The method of  claim 1 , wherein the radiation is UV light. 
     
     
       8. The method of  claim 1 , wherein the one or more nozzles comprises a plurality of nozzles.